%0 Journal Article
%A Topi Urponen
%T On regular expressions over one letter and on commutative languages
%J Annales Fennici Mathematici
%D 1972
%V 501-520
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1972.517/
%R 10.5186/aasfm.1972.517
%G en
%F AFM_1972_501-520_a3